432 research outputs found
Cobb-Douglas Based Firm Production Model under Fuzzy Environment and its Solution using Geometric Programming
In this paper, we consider Cobb-Douglas production function based model in a firm under fuzzy environment, and its solution technique by making use of geometric programming. A firm may use many finite inputs such as labour, capital, coal, iron etc. to produce one single output. It is well known that the primary intention of using production function is to determine maximum output for any given combination of inputs. Also, the firm may gain competitive advantages if it can buy and sell in any quantities at exogenously given prices, independent of initial production decisions. On the other hand, in reality, constraints and/or objective functions in an optimization model may not be crisp quantities. These are usually imprecise in nature and are better represented by using fuzzy sets. Again, geometric programming has many advantages over other optimization techniques. In this paper, Cobb-Douglas production function based models are solved by applying geometric programming technique under fuzzy environment. Illustrative numerical examples further demonstrates the feasibility and efficiency of proposed model under fuzzy environment. Conclusions are drawn at last
Ionic liquids make DNA rigid
Persistence length of dsDNA is known to decrease with increase in ionic
concentration of the solution. In contrast to this, here we show that
persistence length of dsDNA increases dramatically as a function of ionic
liquid (IL) concentration. Using all atomic explicit solvent molecular dynamics
simulations and theoretical models we present, for the first time, a systematic
study to determine the mechanical properties of dsDNA in various hydrated ionic
liquids at different concentrations. We find that dsDNA in 50 wt% ILs have
lower persistence length and stretch modulus in comparison to 80 wt% ILs. We
further observe that both persistence length and stretch modulus of dsDNA
increase as we increase the ILs concentration. Present trend of stretch modulus
and persistence length of dsDNA with ILs concentration supports the predictions
of the macroscopic elastic theory, in contrast to the behavior exhibited by
dsDNA in monovalent salt. Our study further suggests the preferable ILs that
can be used for maintaining DNA stability during long-term storage.Comment: 16 pages, 3 figures, Supplementary Information (Accepted for
publication in the Journal of Chemical Physics, AIP (USA)
ScaleResolving Simulations of a Fundamental TrailingEdge Cooling Slot Using a DiscontinuousGalerkin SpectralElement Method
The accurate prediction of turbulent mixing in high-pressure turbines that incorporate various airfoil surface-cooling strategies is becoming increasing critical to the design of modern gas turbine engines where the quest for improved efficiency is driving compressor overall pressure ratios and turbine inlet temperatures to much higher levels than ever before. In the present paper, a recently developed computational capability for accurate and efficient scaleresolving simulations of turbomachinery is extended to study the turbulent mixing mechanism of a simplified abstraction of an airfoil trailing-edge cooling slot - a plane wall jet with finite lip thickness discharging into an ambient flow. The computational capability is based on an entropy stable, discontinuousGalerkin approach that extends to arbitrarily high orders of spatial and temporal accuracy. The numerical results show that the present simulations capture the trends observed in the experiments. Discrepancies between the simulations and experiments are believed to be due to differences in the inflow profiles and tunnel sidewall effects. The thick lip configuration leads to a thicker wake and higher unsteadiness in the wall jet compared to the thin lip. A detailed comparison of the turbulent flowfields is presented to highlight differences arising due to lip thickness variations
New limit for the half-life of double beta decay of Zr to the first excited state of Mo
Neutrinoless Double Beta Decay is a phenomenon of fundamental interest in
particle physics. The decay rates of double beta decay transitions to the
excited states can provide input for Nuclear Transition Matrix Element
calculations for the relevant two neutrino double beta decay process. It can be
useful as supplementary information for the calculation of Nuclear Transition
Matrix Element for the neutrinoless double beta decay process. In the present
work, double beta decay of Zr to the excited state of
Mo at 871.1 keV is studied using a low background 230 cm HPGe
detector. No evidence of this decay was found with a 232 g.y exposure of
natural Zirconium. The lower half-life limit obtained for the double beta decay
of to the excited state of is y at 90% C.L., an improvement by a factor of
4 over the existing experimental limit at 90\% C.L. The sensitivity is
estimated to be y at 90% C.L. using
the Feldman-Cousins method.Comment: 11 pages, 7 figures, Accepted in Eur. Phys. J.
Distribution of dwell times of a ribosome: effects of infidelity, kinetic proofreading and ribosome crowding
Ribosome is a molecular machine that polymerizes a protein where the sequence
of the amino acid residues, the monomers of the protein, is dictated by the
sequence of codons (triplets of nucleotides) on a messenger RNA (mRNA) that
serves as the template. The ribosome is a molecular motor that utilizes the
template mRNA strand also as the track. Thus, in each step the ribosome moves
forward by one codon and, simultaneously, elongates the protein by one amino
acid. We present a theoretical model that captures most of the main steps in
the mechano-chemical cycle of a ribosome. The stochastic movement of the
ribosome consists of an alternating sequence of pause and translocation; the
sum of the durations of a pause and the following translocation is the time of
dwell of the ribosome at the corresponding codon. We derive the analytical
expression for the distribution of the dwell times of a ribosome in our model.
Whereever experimental data are available, our theoretical predictions are
consistent with those results. We suggest appropriate experiments to test the
new predictions of our model, particularly, the effects of the quality control
mechanism of the ribosome and that of their crowding on the mRNA track.Comment: This is an author-created, un-copyedited version of an article
accepted for publication in Physical Biology. IOP Publishing Ltd is not
responsible for any errors or omissions in this version of the manuscript or
any version derived from it. The definitive publisher authenticated version
is available online at DOI:10.1088/1478-3975/8/2/02600
The role of 99mTc-DTPA retrobulbar SPECT in staging and follow-up of Graves’ orbitopathy
The pathogenesis of Graves’ orbitopathy (GO) is not completely understood. Coexistent hyperfunction of the thyroid gland is frequent; however, GO may also coexist with hypo- or euthyrodism. The course of GO is largely independent of thyroid function, although elevated serum TSH is known to negatively interfere with GO course. GO is severe in 10% of the cases; sight threatening complications may also develop. A successful therapy of GO requires the assesment of both the severity and activity of orbital inflammation. Based on relevant studies and our own experiences, the possible management choices are reviewed here. For this purpose, we compare the clinical value of imaging techniques for detecting the activity of the disease. During the last 15 years, we used 99mTc-DTPA retrobulbar SPECT routinely in more than 1400 patients to facilitate the right therapeutic decision. This diagnostic utility simplified management decisions compared to previously applied alternative techniques. We recommended the routine use of 99mTc-DTPA retrobulbar SPECT for the evaluation and follow-up of GO.The pathogenesis of Graves’ orbitopathy (GO) is not completely understood. Coexistent hyperfunction of the thyroid gland is frequent; however, GO may also coexist with hypo- or euthyrodism. The course of GO is largely independent of thyroid funcÂtion, although elevated serum TSH is known to negatively interfere with GO course. GO is severe in 10% of the cases; sight threatening complications may also develop. A successful therapy of GO requires the assesment of both the severity and activity of orbital inflammation. Based on relevant studies and our own experiences, the possible management choices are reviewed here. For this purpose, we compare the clinical value of imaging techniques for detecting the activity of the disease. During the last 15 years, we used 99mTc-DTPA retrobulbar SPECT routinely in more than 1400 patients to facilitate the right therapeutic decision. This diagnostic utility simplified management decisions compared to previously applied alternative techniques. We recommended the routine use of 99mTc-DTPA retrobulbar SPECT for the evaluation and follow-up of GO.
Scale-Resolving Simulations of Low-Pressure Turbine Cascades with Wall Roughness Using A Spectral-Element Method
The accurate prediction of wall-roughness effects in turbomachinery is becoming critical as turbine designers address airfoil surface quality and degradation concerns arising from the shift to advanced ceramic matrix composite (CMC) or additively-manufactured airfoils operating in higher temperature environments. In this paper, a recently developed computational capability for accurate and efficient scale-resolving simulations of turbomachinery is extended to analyze the boundary- layer separation and transition characteristics in a rough-wall low-pressure turbine (LPT) cascade. The computational capability is based on an entropy-stable discontinuous-Galerkin spectral-element approach that extends to arbitrarily high orders of spatial and temporal accuracy, and is implemented in an efficient manner for a modern high performance computer architecture. Results from the scale-resolving simulations of both smooth and rough airfoil cascades are presented and compared to previous experiments and numerical simulations. The results show that the suction surface boundary layer undergoes laminar separation, transition, and turbulent reattachment for the smooth airfoil cascade, while in the presence of roughness the separation and transition behavior of the suction surface boundary layer is substantially modified. The differences between the smooth and rough airfoil cascades are then highlighted by a detailed analysis of their respective turbulent flow fields
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